No-post-cure method of curing polyacrylate polymers

ABSTRACT

A no-post-cure method of curing polyacrylates having dual cure sites is accomplished with a two-part curing system or a combined one-part curing system. The two-part curing system consists of one of more metallic acid salts and an ammonium and/or phosphonium quaternary salt. The one-part curing system consists of an ammonium or phosphonium quaternary acid salt. The polyacrylate rubber must have both a halogen and a carboxyl cure site. The method consists of blending the curative with the polyacrylate rubber and heating the resultant composition until the composition cures. Because the mixed composition is shelf stable, it is not necessary to immediately heat the composition to cure it. The method may optionally include the step of storing the mixed composition until it is desired to cure it.

CROSS-REFERENCE

This application is a continuation of U.S. Ser. No. 07/227/396, filedAug. 4, 1988, now abandoned for "No-Post-Cure Method of CuringPolyacrylate Polymers," which is in turn a continuation-in-part of U.S.Ser. No. 101,883, filed Sept. 28, 1987, now abandoned for "No-Post-CureMethod of Curing Polyacrylate Polymers."

FIELD OF THE INVENTION

The present invention pertains to a no-post-cure method for curingpolyacrylates having dual cure sites. The cure system consists of asubstituted ammonium and/or phosphonium quaternary salt and sometimes anacid acceptor such as an alkali metal salt. The no-post-cure method ofthe present invention is unique because the polyacrylate rubber, whenadmixed with the proper amount of the curative, has an extremely longshelf stability so long as it is maintained below the thresholdtemperature range. When it is desired to cure the polyacrylate polymershaving the curative admixed therein, one merely has to raise thetemperature to within the threshold temperature range.

BACKGROUND ART

Processes are known for curing polyacrylate polymers having dual curesites by employing quaternary ammonium salts, for example, as acurative. Exemplary of methods for curing polyacrylate polymers are thefollowing three U S. patents.

U.S. Pat. No. 3,875,092 to Morris discloses acrylate rubbers having bothhalogen and carboxyl cure sites which are vulcanized using as the onlycuring agent a quaternary ammonium salt. The vulcanized compositionsexhibit good physical properties and low press-cured and post-curedcompression sets.

U.S. Pat. No. 3,912,672 to Morris et al discloses a cure system for dualcure site acrylate rubbers. The acrylate rubbers have both halogen andcarboxyl cure sites and are vulcanized using an alkali metal salt of acarboxylic acid or an organo-phosphoric acid. The alkali metal salt maybe sodium or potassium stearate. The vulcanization can also occur withthe addition of a quaternary ammonium salt or an amine to catalyze thevulcanization.

U.S. Pat. No. 3,976,610 to Morris, et al, discloses acrylate rubbershaving both halogen and carboxyl cure sites which are vulcanized usingan alkali metal salt of a carboxylic or organo-phosphoric acid and anamine-blocked isocyanate. The alkali metal salt may be sodium orpotassium stearate. Like the other polyacrylate vulcanizablecompositions, these compositions exhibit low press-cured and post-curedcompression sets.

None of the above mentioned patents describe a no-post-cure process anddo not recognize a temperature threshold effect for polyacrylaterubbers. The following patent does briefly mention the possibility of ano-post-cure process.

U.S. Pat. No. 4,650,834 to Yagishita, et al, describes a vulcanizableelastomer containing an epoxy group as the cure site. The vulcanizableepoxy elastomer also includes a carboxylic acid having at least twocarboxyl groups in the molecule. The curative for vulcanizing theelastomer may be either a quaternary ammonium or phosphonium salt. Whilethis patent does mention the possibility of omitting a post-curingstage, none of the examples omit the post-cured stage. Moreover, thisreference is completely silent with respect to a good shelf stabilityand a temperature threshold.

These above references are exemplary of curing processes which requireabout a 15 to 20 hour post-cure time (even Yagishita, et al, employed a16 hour post-cure). Acrylate rubbers exhibit favorable qualities ofweatherability, high temperature serviceability, and good oilresistance. These qualities make the rubbers useful for automotive andnon-automotive applications such as industrial and out-of-doorapplications. Their use is limited by the tendency of the vulcanizatesto post-cure during use. This results in property change and in somecases in failure of the article. To overcome these problems, theacrylate rubber vulcanizates are purposely post-cured, often as long as24 hours or more, to obtain a more complete cure. This is shown by areduced compression set. It would be of great advantage to the industryto reduce or eliminate the time required for post-cure. It is of furtheradvantage that the acrylate compounds have long shelf stability. In thepast, processing such as compression, injection, or transfer molding;steam autoclave; continuous vulcanization (CV) cure techniques, and thelike, have been limited by slow cure and poor shelf stability. Theseproblems are solved by the present invention.

SUMMARY OF THE INVENTION

The no-post-cure method of curing polyacrylates having dual cure site isaccomplished using a specific two-part curing system or a combinedone-part curing system. The two-part curing system consists of metallicacid salt, and particularly sodium and potassium stearate, along with analkyl substituted ammonium and/or phosphonium quaternary salt. Thepolyacrylate rubber must have both a halogen and a carboxyl cure site.The ammonium and/or phosphonium salt have the following formula:##STR1## wherein Q is nitrogen or phosphorous, wherein R₁, R₂, R₃ and R₄are hydrocarbon radicals, and wherein X is an anion of an organic orinorganic acid wherein the acidic hydrogen is attached to a halogen oran oxygen atom, and in particular wherein X is a halogen or alkyl,alkaryl or alkoxy acid of the group carboxylic, phosphoric and sulfuricacid.

The two-part curing system consists of a metallic acid salt and aquaternary salt, as described previously. It is believed that when thetwo-part curing system is uniformly blended and "reacted", the anionfrom the quaternary salt reacts with the metallic acid salt to form aquaternary acid salt. An example is presented by the following equation:##STR2##

Therefore, a one-part curing system may also be employed in the presentinvention if the quaternary salt is an acid salt as defined above. As anexample, X⁻ can be a stearate RCOO⁻ and preferably C₁₇ H₃₅ COO⁻.

In the broadest sense, the present invention consists of a no-post-curemethod of curing a dual site (halogen/carboxyl) polyacrylate elastomerby employing a cure system having an acid such as a metallic acid saltor an organo phosphoric acid and an ammonium and/or phosphoniumquaternary salt by blending these components into a uniform compositionat a temperature below the threshold or activation temperature range,and heating the composition to within or above the activation orthreshold temperature range to cure the polyacrylate elastomer. Thequaternary salt could be an acid salt such as a stearate salt.

DETAILED DESCRIPTION

Acrylate rubbers of the present invention which can be cured without apost-cure system are interpolymers comprising acrylate monomer(s), areactive halogen-containing monomer, and a carboxyl-containing monomer.

The acrylate rubber contains from about 40% to about 99.8% by weight,based upon the weight of the polymer, of an acrylate of the formula:##STR3## wherein R is an alkyl radical containing 1 to 8 carbon atoms,an alkoxyalkyl or alkylthioalkyl radical containing 2 to about 12 carbonatoms. The alkyl structure can contain primary, secondary, or tertiarycarbon configurations. Examples of such acrylates are methyl acrylate,ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate,n-pentyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-methyl-pentylacrylate, n-octyl acrylate, 2-ethylhexyl acrylate, n-decyl acrylate,n-dodecyl acrylate, n-octadecyl acrylate, and the like; methoxymethylacrylate, methoxyethyl acrylate, ethoxyethyl acrylate, butoxyethylacrylate, ethoxypropyl acrylate, methylthioethyl acrylate,hexylthioethyl acrylate, and the like; and α,β-cyanoethyl acrylate, α,β-and δ-cyanopropyl acrylate, cyanobutyl acrylate, cyanohexyl acrylate,cyanooctyl acrylate, and the like. Often mixtures of two or moremonomers and/or types of acrylate monomers can be employed.

Preferably, the rubber contains from about 65% to about 99.6% by weightof acrylates of the formula set forth previously, wherein R is an alkylradical containing 1 to about 10 carbon atoms or an alkoxyalkyl radicalcontaining 2 to about 8 carbon atoms. Examples of the more preferredacrylates are ethyl acrylate, propyl acrylate, n-butyl acrylate, hexylacrylate, 2-ethylhexyl acrylate, octyl acrylate, and the like, andmethoxyethyl acrylate, ethoxyethyl acrylate, and the like. Both an alkylacrylate and an alkoxyalkyl acrylate can be used.

The rubber contains from about 0.1% to about 30% by weight of an activehalogen-containing monomer. The halogen groups can be chlorine, bromine,or iodine. Examples of such monomers are vinyl chloroacetate, vinylbromoacetate, allyl chloroacetate, vinyl chloropropionate, vinylchlorobutyrate, vinyl bromobutyrate, 2-chloroethyl acrylate,3-chloropropyl acrylate, 4-chlorobutyl acrylate, 2-chloroethylmethacrylate, 2-bromoethyl acrylate, 2-iodoethyl acrylate, 2-chloroethylvinyl ether, chloromethyl vinyl ketone, 4-chloro-2-butenyl acrylate,vinyl benzyl chloride, 5-chloromethyl-2-norbornene,5-α-chloroacetoxymethyl)-2-norbornene,5-(α,β-dichloropropionylmethyl)-2-norbornene, and the like. Thepreferred monomers are vinyl chloroacetate, allyl chloroacetate,2-chloroethyl acrylate, 2-chloroethyl vinyl ether, vinyl benzylchloride, 5-chloromethyl-2-norbornene, and5-chloroacetoxymethyl-2-norbornene.

More preferably, the rubber contains from about 0.2% to about 15% byweight of the active halogen-containing monomer. At this level, thehalogen content is from about 0.1% to about 5% by weight of the rubber.Due to the availability and cost, the chlorine-containing monomers arepreferred.

The rubbers also contain from about 0.1% to about 20% by weight of acarboxyl-containing monomer. The monomer can be monocarboxylic orpolycarboxylic, containing from 3 to about 8 carbon atoms. Examples ofsuch monomers are acrylic acid, methacrylic acid, ethacrylic acid,β,β-dimethylacrylic acid, crotonic acid, 2-pentenoic acid, 2-hexenoicacid, maleic acid, furmaric acid, citraconic acid, mesaconic acid,itaconic acid, 3-butene-1,2,3-tricarboxylic acid, and the like.

More preferably the rubber contains from 0.2% to about 10% by weight ofthe carboxyl-containing monomer. At this level, the carboxyl content isfrom about 0.1% to about 7% by weight of the rubber. The more preferredmonomers are the monocarboxylic acid monomers such as acrylic acid,methacrylic acid, itaconic acid, and the like.

The rubber can contain up to about 35% and preferably up to about 10% byweight of other copolymerizable vinylidene monomers having a terminalvinylidene ##STR4## group. Examples of such are phenyl acrylate,cyclohexyl acrylate, methacrylates such as methyl methacrylate, ethylmethacrylate, and the like; vinyl and allyl esters such as vinylacetate, vinyl propionate, allyl acetate, and the like; vinyl ketonessuch as methyl vinyl ketone; vinyl and allyl ethers such as vinyl methylether, vinyl ethyl ether, allyl methyl ether, and the like; vinylaromatics such as styrene, α-methyl styrene, vinyl toluene, and thelike; vinyl nitriles such as acrylonitrile and methacrylonitrile;vinylamides such as acrylamide, methacrylamide, N-methyl methacrylamide,and the like; and dienes and divinyls such as butadiene, isoprene,divinyl benzene, divinyl ether, diethylene glycol diacrylate, and thelike. The more preferred copolymerizable monomers are vinyl acetate,methyl methacrylate, ethyl methacrylate, styrene, acrylonitrile,acrylamide, divinyl benzene, and diethylene glycol diacrylate.

The acrylate rubbers can be prepared using emulsion (latex), suspension,solution and bulk techniques known to those skilled in the art. Becauseit is desirable to polymerize the monomers to 90% conversion or over,emulsion and suspension techniques are usually employed. Thepolymerization can be performed as a batch reaction or one or moreingredients can be proportioned during the manufacturing process.Temperature of polymerization ranges from about -10° C. to about 100°C., whereas a more preferred range is from about 5° C. to about 80° C.

The polymerization can be initiated by free-radical generating agents.Examples of such agents are organic peroxides and hydroperoxides such asbenzoyl peroxide, dicumyl peroxide, cumene hydroperoxide, paramethanehydroperoxide, and the like, used alone or with redox systems; diazocompounds such as azobisisobutyronitrile, and the like; persulfate saltssuch as sodium, potassium, and ammonium persulfate, used alone or withredox systems; and the use of utraviolet light with photo-sensitiveagents such as benzophenone, triphenylphosphine, organic diazos, and thelike.

Typical emulsion polymerization ingredients would include a persulfatesalt or organic peroxide and usually a redox system, water adjusted tothe desired pH with acids or basis and usually buffered with inorganicsalts, and either anionic, cationic, or nonionic surface active agentswell known in the art.

The polymerization normally is continued until about 90% conversion ofthe monomers is obtained. The resulting latex (if the emulsion processis employed) can be coagulated to isolate the polymer. Typicalcoagulation procedures are salt-acid coagulations, use of polyvalentmetal salts such as magnesium sulfate (MgSO₄) or calcium chloride, useof alcohols such as methanol, isopropyl alcohol, and freezeagglomeration techniques. The rubber is then usually washed with waterand dried.

The acrylate rubbers have raw polymer Mooney values (ML-4 at 212° F.)from about 20 to about 100.

The rubbers are admixed with cure ingredients and compoundingingredients using conventional equipment such as a Banbury mixer,extruders, and the like.

When preparing a vulcanizable composition, the polymer is mixed with thecuring agents in the Banbury mixer, or other conventional equipment. Thevulcanizable composition, in addition to the curing system and thepolymers, may also include conventional carbon blacks, other fillers,antioxidants, emulsifiers, plasticizers, retarders, accelerators, andthe like conventionally known in the art.

The two-part cure system of the present invention consists of a metallicacid salt and an alkyl substituted ammonium and/or phosphoniumquaternary salt. The metallic acid salt can be a carboxylic acidcontaining from 2 to about 24 carbon atoms and organophosphorus acids ofthe formula

    (R--O).sub.z PO.sub.y M

where M is an alkali metal, y equals 1 or 2, z equals 1 or 2, and y plusz equals 3, and R is selected from the group consisting of alkylradicals containing from 1 to about 24 carbon atoms, and an aryl radicalcontaining from 6 to about 24 carbon atoms. Specific examples ofsuitable metallic acid salts include carboxylic acid salts such asstearic, acetic, butyric, lauric, palmetic, oleic, benzoic acids; andorganophosphoric acid salts such as alkylphenoxy poly(ethyleneoxy) ethylphosphate. More specific acid salts include sodium stearate, potassiumstearate, copper stearate, or the like.

The substituted ammonium and/or phosphonium quaternary salts are saltsin which all four hydrogen atoms of ammonium or phosphonium have beenreplaced with organic radicals. The quaternary ammonium or phosphoniumsalts have the structure ##STR5## wherein Q is nitrogen or phosphorous,wherein R₁, R₂, R₃ and R₄ are hydrocarbon radicals containing 1 to about18 carbon atoms such as alkyl, aryl, alkaryl, aralkyl radicals, orwherein two or three of the R₁, R₂, R₃ and R₄ form with the nitrogen orphosphorous atom a heterocyclic structure containing 3 to 8 atomsselected from the group consisting of carbon, nitrogen, oxygen andsulfur wherein at least two atoms are carbon; and X is an anion of anorganic or inorganic acid wherein the acidic hydrogen is attached to ahalogen or an oxygen atom, and in particular wherein X is a halogen oralkyl, alkaryl or alkoxy acid of the group carboxylic, phosphoric andsulfuric acid. More specific examples of such anions include chlorine(Cl⁻), bromine (Br⁻), iodine (I⁻), or hydroxide (OH⁻), sulfuric acid(HSO₄), phosphoric acid (H₂ PO₄), carboxylic acid (RCOO⁻),organosulfuric acid (ROSO₃ or RSO₃ ), and organo-phosphoric acid (ROPO₃H) where in the last examples R is an alkyl or alkaryl radicalcontaining from 1 to about 18 carbon atoms.

In the one-part cure system of the present invention, the metallic acidsalt is not employed and the ammonium or phosphonium quaternary saltmust be a carboxylic or organophosphoric acid salt. Specifically thecurative is an ammonium or phosponium quaternary acid salt wherein theacid is either a carboxylic acid containing from 2 to about 24 carbonatoms or an organophosphorus acid of the formula

    (R--O).sub.z PO.sub.y M

where M is the ammonium or phosphorium quaternary salt, y equals 1 or 2,z equals 1 or 2, and y plus 2 equals 3, and R is selected from the groupconsisting of alkyl radicals containing from 1 to about 24 carbon atoms,and an aryl radical containing from 6 to about 24 carbon atoms.Preferably, in the one-part cure system, X is a stearate ion of theformula RCOO⁻, and more preferably C₁₇ H₃₅ COO⁻. The preferredquaternary ammonium or phosphonium stearate salt has the followingformula: ##STR6## wherein Q is nitrogen or phosphorous, and wherein R₁,R₂, R₃, and R₄ are the same as previously stated.

Examples of quaternary ammonium salts for the two-part cure system aretetramethyl ammonium chloride, tetramethyl ammonium bromide,trimethylethyl ammonium iodide, trimethylsoya ammonium chloride,trimethylcetyl ammonium bromide, trimethylbenzyl ammonium chloride,dimethylethylcetyl ammonium chloride, dimethyloctylbenzyl ammoniumchloride, dimethyloleyl benzyl ammonium chloride,dimethyloctadecylbenzyl ammonium chloride, dimethylphenylbenzyl ammoniumbromide, dimethyldibenzyl ammonium bromide, methylethylpropylisobutylammonium chloride, (tetradecyl)trimethyl ammonium chloride,methylcetyldibenzyl ammonium bromide, cetylpyridinium chloride,dodecylpyridinium bromide, tetrabutyl ammonium chloride, tetrabutylammonium bromide, tetrabutyl ammonium iodide, tetramethyl ammoniumhydroxide pentahydrate, cetyldimethylethyl ammonium bromide,cetyltrimethyl ammonium-p-toluenesulfonate, myristyltrimethyl ammoniumbromide, and the like.

Examples of quaternary phosphonium salts for the two-part cure systemare tetraphenyl phosphonium bromide, hexadecyltributyl phosphoniumbromide, tetraphenyl phosphonium chloride, tetraphenyl phosphoniumiodide, tetrabutyl phosphonium chloride, tetrabutyl phosphonium bromide,triphenylbenzyl phosphonium chloride, triphenylbenzyl phosphoniumbromide, triphenylbenzyl phosphonium iodide, triphenylmethoxymethylphosphonium chloride, triethylbenzyl phosphonium chloride,tricyclohexylbenzyl phosphonium chloride, and the like.

Examples of quaternary ammonium or phosphonium acid salts employed asthe one-part curative are trimethylbenzyl ammonium stearate,trimethylbenzyl phosphonium stearate, trimethylsoya ammonium stearate,trimethylsoya phosphonium stearate, tetramethyl ammonium stearate,tetramethyl phosphonium stearate, cetyltrimethyl ammonium stearate,cetyltrimethyl phosphonium stearate, tetrabutyl ammonium stearate,dimethylphenylbenzyl ammonium stearate, dimethylphenylbenzyl phosphoniumstearate, alkylphenoxypoly(ethyleneoxy)ethyl phosphate, and the like.

These quaternary ammonium or phosphonium salts may be used singlely oras a mixture of two or more. The amount of the quaternary ammonium orphosphonium salt is usually 0.1 to 20 parts by weight per 100 parts byweight of the polymer, and preferably 1 to 4 parts. The metallic acidsalt employed in the two-part cure system is in the range of 0.1 to 10parts by weight per 100 parts by weight of the polymer, and preferably2-6 parts. These ranges have been selected for high vulcanization orcuring speeds and excellent processing stability and long term storagestability of the vulcanizable composition with excellent mechanicalproperties and compression sets when the vulcanizable composition iscured. If the amount of metallic acid salt and quaternary salt is belowthe specified ranges, vulcanization or curing proceeds very slowly suchthat it is almost nonexistent. On the other hand, if the amount ofmetallic acid salt and quaternary salt is above these ranges, the curingor vulcanization speed is extremely fast, allows no processing time andis very scorchy. Additionally, the mechanical properties and thecompression sets are greatly reduced.

As previously mentioned, these ingredients may be mixed withconventional equipment such as a Banbury mixer.

As an aspect of the present invention the composition utilized in thepresent process has "threshold temperature characteristics." By thisterm it is meant that once a uniform composition has been obtained, thevulcanizable composition will remain shelfstable over long periods oftime so long as it is maintained below the threshold temperature.However, once the composition is subjected to this temperature, it willcure relatively rapidly and completely so that a post cure step is notnecessary. More specifically, the composition will have a relatively lowrate of cure as shown by a low minimum viscosity change over time aslong as the composition is maintained below the threshold temperature.In particular, the method of the invention results in a vulcanizablecomposition having a minimum viscosity change of less than 150 Mooneyunits over a two-week period as measured by the Mooney Viscometer LargeRotor Test ASTM D1646 at 100° C., and preferably of less than 5 MooneyUnits over an eight-week period. However, once the composition issubjected to the threshold temperature, the composition will curerelatively rapidly. The "threshold temperature" criteria means atemperature at which the t₅ value measured by the Mooney ViscometerLarge Rotor Test (ASTM D1646) increases by 5 points or more in 31minutes. Moreover, in accordance with the present invention attemperatures above the threshold temperature, the cure will berelatively complete as to eliminate the need for a post-cure step. Thecompleteness of the curing step without the prior art post-cure step isshown by a compression set after 70 hours at 150° C., plied, percent(ASTM Test D395), by equal or less than 80 and preferably equal or lessthan 40.

The threshold temperature varies for each combination of metallic acidsalt and quaternary salt employed. However, the preferred two-partcurative is shelf stable if maintained below about 50° C. Generally, forthe preferred curatives the threshold temperature ranges from about 90°C. to about 150° C. Above 150° C., most of the vulcanizable compositionscured extremely fast and would be too scorchy to process.

Although it was mentioned previously that the vulcanization rate may beextremely fast if the amount of curative employed is above a certainpreferred range, the upper limit of this range may be extended ifconventional acrylate polymer retarders are employed. If retarders areemployed, the vulcanization rate can be reduced. However, if employinggreatly excessive amounts of curative with copious amounts of retarder,the vulcanization rate may be reduced but the physical properties of theresultant polymer are very poor. The best physical properties areobtained when very little retarder is employed. Conventional retardersfor polyacrylate polymers are acids, such as citric acid, acetic acid,stearic acid, and the like.

EXAMPLE 1

This example demonstrates the shelf stability of a vulcanizablecomposition. The following ingredients were uniformly mixed in a Banburymixer at room temperature (25° C.).

    ______________________________________               Parts by Wt. Based    Ingredients               Upon 100 phr.  Description    ______________________________________    Polyacrylate               100                Polyacrylate with    rubber                        dual cure site                                  chloride/carboxyl    Stearic Acid               1                  Retarder, lubricant    Struktol WB-222               2                  Ester of saturated                                  fatty acid, process                                  aid    N 550, FEF 75                 Carbon black filler    Agerite*   2                  Octylated diphenyl    Stalite S                     amine, antioxidant    Thiokol TP-759               6                  Ether/ester,                                  plasticizer    Total      186    parts by weight    ______________________________________

To 186 parts of the total blend, 5 parts of curative were added, namely:sodium stearate 4 parts by weight, and cetyltrimethyl ammonium bromide 1part by weight, for a total vulcanizable composition of 191 parts byweight. Once the composition was uniformly mixed by a two roll mill, theMooney viscosity was determined using a large rotor at 93° C. and 125°C. Additionally, the same vulcanizable composition was tested eightweeks later during which time the sample was maintained at roomtemperature (25° C.). During testing, the vulcanizable composition wasagain tested at 93° C. and 125° C. The results are set forth below andindicate that the Mooney viscosity (large rotor) changes very littleduring the eight week time period thereby indicating a very stable shelflife.

    ______________________________________    Mooney Viscosity, (Large Rotor)           As Is  Remilled  As Is     Remilled    ______________________________________                        93° C. 8           93° C. Original                        Wks. Room Temp. Aging    Min. Visc.             62       49        69      45    t.sub.5 min.             23.5     16.75     >31     16    t.sub.35 min.             >31      >31       >31     >31                        125° C. 8           125° C. Original                        Wks. Room Temp. Aging    Min. Visc.             65       52        74      44    t.sub.5 min.             2.5      2.25      3.5     2.5    t.sub.35 min.             >31      8.5       >31     4.5    ______________________________________

The fact that the t₅ and t₃₅ scorch times do not show any significantdifference after eight weeks is indicative of the excellent shelf life.

EXAMPLE 2

This example further demonstrates the shelf stability of a vulcanizablecomposition. The following ingredients were uniformly mixed in a Banburymixer at room temperature (25° C.).

    ______________________________________                       Parts by Weight Based    Ingredients        Upon 100 phr    ______________________________________    Polyacrylate rubber                       100    Stearic acid       1    N550, FEF          65    Agerite Stalite S  2    Sodium Stearate    4    Cetyltrimethyl ammonium bromide                       1    ______________________________________

Once the composition was uniformly mixed by a two-roll mill, the Mooneyviscosity was determined using a large rotor at 85° C., 100° C., and125°. Corresponding Mooney viscosity readings were taken every two weeksafter room temperature aging for an eight week period. Further, aRheometer oscillating disc test was run at 190° C. with a 3° arc. Theminimum (M_(L)) point, maximum (M_(HF)) point, and cure point (t₉₀) wererecorded. (Where unspecified later, the same test parameters are used).The results of the tests are set forth below.

    ______________________________________    MOONEY VISCOSITY (Large Rotor)    Test Week            0          2           4    6     8    ______________________________________    85° C.    min. visc.            73         65          --   --    --    t.sub.5, (min.)            27         >30         --   --    --    t.sub.35, (min.)            >>30       >>30        --   --    --    100° C.    min. visc.            60         52          56   55    56    t.sub.5, (min.)            8.0        8.0         9.5  9.0   9.5    t.sub.35, (min.)            13.3       13.5        16.5 15.0  15.5    125° C.    min. visc.            51         45          --   --    --    t.sub.5, (min.)            2.5        2.5         --   --    --    t.sub.35, (min.)            3.5        3.5         --   --    --    ______________________________________    Rheometer Microdie, 100 cpm, 3° Arc, 190° C.    M.sub.L (lbf-in)             7.5    M.sub.HF (lbf-in)             61.8    t'.sub.90, min.             3.8

EXAMPLE 3

This example demonstrates a large number of ammonium or phosphoniumquaternary salts having halogen or hydroxide reactive groups aretemperature sensitive, i.e., are shelf stable below temperature range,but can cure with good mechanical and compression set properties withoutpost curing being necessary so long as curing occurs within thethreshold temperature range.

    ______________________________________    A Master Batch       Level    ______________________________________    Polyacrylate rubber having halogen                         100     parts by wt.    and carboxyl dual cure sites    Stearic Acid (lubricant and retarder                         1    Struktol WB-222 (fatty soap, processing                         2    aid)    Philblack N 550 (carbon black, filler)                         65    Stalite S (octylated diphenyl amine,                         2    antioxidant)    ______________________________________

The master batch was uniformly mixed in a Banbury mixer. 400 grams ofthe master batch was then blended with sodium stearate, 9.4 grams (4parts), and cetyltrimethyl ammonium bromide, 2.35 grams (the equivalentof 1 part per 100 parts of polymer). The cetyltrimethyl ammonium bromidewas replaced with other curatives set forth below. All curatives wereused at the same molar level. Accordingly, depending upon the molecularweight of the curative, the curative would not necessarily be employedat 1 part per 100 parts of rubber as set forth for the cetyltrimethylammonium bromide.

The curatives employed were:

1. Cetyltrimethyl ammonium bromide,

2. Tetrabutyl ammonium chloride,

3. Tetrabutyl ammonium bromide,

4. Tetrabutyl ammonium iodide,

5. Tetraphenyl phosphonium bromide,

6. Hexadecyltributyl phosphonium bromide,

7. Tetramethyl ammonium hydroxide pentahydrate,

8. Cetyldimethylethyl ammonium bromide,

9. Tetraphenyl phosphonium chloride,

10. Tetraphenyl phosphonium iodide,

11. Tetrabutyl phosphonium chloride,

12. Tetrabutyl phosphonium bromide,

13. Cetyl trimethyl ammonium-p-toluenesulfonate,

14. Myristyltrimethyl ammonium bromide.

As soon as the curatives were uniformly blended with the master batch, aRheometer microdie oscillating disc test was run at 100 cpm, 190° C.with 3° arc. The minimum (M_(L)) point, maximum (M_(HF)) point, and curepoint (t₉₀), the time when 90% of the torque change was achieved, wererecorded for the twelve curative systems. Additionally, a Mooneyviscosity and a t₅ and t₃₅, in minutes, were conducted at 100° C. and125° C. The results of those tests are as set forth below.

    __________________________________________________________________________                  1  2   3   4   5  6   7  8  9  10 11  12    __________________________________________________________________________    Rheometer M.sub.L                  7.4                     8.1 11  8.7 7.0                                    9.0 9.8                                           10 9.8                                                 5.8                                                    10  13              (lbf-in)    190° C., 3°Arc              M.sub.HF                  58 47.8                         60.5                             67  65 58.8                                        65.4                                           62.3                                              58 59.2                                                    63.2                                                        70.2              (lbf-in)              t'.sub.90                  4.8                     7.4 3.5 1.5 6.0                                    5.0 8.8                                           3.5                                              11.8                                                 8.0                                                    11.5                                                        3.4              (min.)    Mooney Viscometer    (Large Rotor)    100° C.              Min.                  49 52  59  59  50.5                                    51.0                                        59 52 53 50.7                                                    60.2                                                        70.5              Visc.              t.sub.5                  9.4                     5.7 3.2 2.7 8.2                                    6.2 5.0                                           6.8                                              5.6                                                 >31                                                    4.3 2.4              (min.)              t.sub.35                  15.2                     9.3 4.3 3.4 12.3                                    9.2 8.8                                           10.7                                              8.6                                                 52*    3.6              (min.)    125° C.              Min.                  40 45  >200                             >200                                 39 45  56 45.5                                              45.7                                                 34 60  >200              Visc.              t.sub.5                  2.5                     2.0         3.2                                    2.2 1.8                                           2.3                                              2.2                                                 8.3                                                    1.6              (min.)              t.sub.35                  3.6                     2.5         4.1                                    2.6 2.3                                           2.9                                              2.8                                                 13.8                                                    2.0              (min.)    100°  C.              Min.                  46.0                     >200                         >200                             >200                                 60.2                                    >200                                        121                                           55.0                                              73.4                                                 47.0                                                    >200    Aged at Room              Visc.    Temp. 2 wks.              t.sub.5                  9.6            4.8    4.3                                           6.5                                              4.2                                                 15.5              (min.)              t.sub.35                  17.3           7.3       11.1                                              6.4                                                 29.4              (min.)    __________________________________________________________________________                                                  13    14    __________________________________________________________________________                             Rheometer, microdie                                          M.sub.L (lbf-in)                                                  6.1   8.4                             100 cpm, 190° C., 3°Arc                                          M.sub.HF (lbf-in)                                                  51.6  66.1                                          t'.sub.90 (min.)                                                  15.0  3.8                                          (min.)                             Mooney Viscometer                             (Large Rotor)                             100° C.                                          Min. Visc.                                                  49    54                                          t.sub.5 (min.)                                                  >31   8.2                                          t.sub.35 (min.)                                                  >31   12.5                             125° C.                                          Min. Visc.                                                  37.2  41.8                                          t.sub.5 (min.)                                                  3.6   2.2                                          t.sub.35 (min.)                                                  5.5   2.8                             125° C. Aged at Room                                          min. vis.                                                  36    44                             Temp. 2 wks. t.sub.5 (min.)                                                  3.4   2.6                                          t.sub.35 (min.)                                                  5.3   3.3    __________________________________________________________________________

As is evident from the above Examples, some of the curatives werequicker than others. The curatives which vulcanize quickly could beemployed along with a retarder to slow down the curing time such thatthere is a longer processing time. The curatives which have a slowprocessing time could be employed in amounts greater than employed inthis example so that the processing time could be greatly reduced. Basedupon the above data, it is clear that many different curatives can beemployed and the processing time can be controlled by the use ofretarders or greater or lesser amounts of the curative itself.

EXAMPLE 4

The original physical properties of the various compounds set forth inExample 3 are set forth in the table below. The physical properties weredetermined by curing the samples for four minutes at 190° C. and thecompression set data was determined after 70 hours at 150° C. The firstphysical property, stress at 100 percent elongation, set forth is theamount of force per unit area (stress) necessary to stretch thevulcanized polymer to 100% of its original elongation according to ASTMD 412. The second physical property tested was its maximum tensile atbreak and the third physical property is the percent elongation atbreak, according to ASTM D 412. The next physical property tested is thehardness according to ASTM D 2240. The last physical property is theplied compression set according to ASTM D 395, method B.

    __________________________________________________________________________        Stress              Ultimate             Compression,        at 100%              Tensile Ultimate     Plied, %        Elongation              Strength                      Elongation                            Hardness                                   (70 Hrs. at    Batch        (PSI) (PSI at Break)                      (Percent)                            Durometer A                                   150° C.)    __________________________________________________________________________    1   700   1720    210   67     39    2   460   1490    300   63     62    3   630   1620    210   63     29    4   800   1810    190   65     19    5   725   1725    200   68     40    6   600   1450    270   63     38    7   700   1825    200   65     42    8   700   1700    200   67     30    9   550   1460    270   65     62    10  710   1835    190   72     43    11  550   1560    270   63     50    12  740   1740    200   63     29    13  1060  1400    300   68     73    14  920   1740    180   69     31    __________________________________________________________________________

Based on Rheometer data, Mooney scorch, aging data and original physicalproperties, the cetyltrimethyl ammonium bromide and cetyldimethylethylammonium bromide provided the best balance of properties for the masterbatch formulation. Again, however, these properties will vary byemploying retarders, etc. to prevent scorchiness and prevulcanization.

EXAMPLE 5

The cetyltrimethyl ammonium bromide was employed to determine the Mooneyscorch time as a function of temperature. The minimum viscosity, the t₅value, t₃₅ value and viscosity at 31 minutes were determined for thecetyltrimethyl ammonium bromide at various temperatures as set forthbelow.

    ______________________________________    Mooney Viscometer, Large Rotor    Temp. °C.             70°                    80°                            85°                                 90°                                       93°                                            100°                                                  125°    ______________________________________    Min. Visc.             81.0   71.6    60.3 54.9  58.0 54.7  46.7    t.sub.5 (min.)             >31    >31     >31  22.8  22.8 8.7   2.8    t.sub.35 (min.)             >31    >31     >31  >31   >31  15.1  3.7    Visc.    81.0   72.0    62.2 67.0  84.2    at 31 minutes    ______________________________________

Based upon the above results, the cetyltrimethyl ammonium bromide in amaster batch formulation having 1 part of retarder incorporated thereinwill begin curing in a temperature range of about 85° C. to 90° C. Belowthis range the cetryltrimethyl ammonium bromide as a curative appears tobe substantially inactive.

A similar test was performed substituting tetramethyl ammonium hydroxidepentahydrate for the cetyltrimethyl ammonium bromide. The minimumviscosity, t₅ value, t₃₅ value and viscosity at 31 minutes weredetermined at various temperatures as set forth below.

    ______________________________________    Mooney Viscometer, Large Rotor    Temp. °C.               75° C.                       80° C.                                85° C.                                      100° C.                                             125° C.    ______________________________________    Min. Visc. 71      66       62    59     56    t.sub.5 (min.)               --      22.2     15.9  5      1.8    t.sub.35 (min.)               --      --       --    8.8    2.3    Visc. at 31 min.               74      74       76    --     --    ______________________________________

Based on the forgoing results, a threshold temperature at which curingbegins is evidenced. The criterion for the temperature range at whichcuring starts is a 5 point or greater rise in the Mooney viscosity after31 minutes. The threshold temperatures for selected curatives are shownbelow.

    ______________________________________                             Threshold                             Temperature    Curative                 Range °C.    ______________________________________    Tetraphenylphosphonium bromide                             80-85    Tetramethyl ammonium hydroxide pentahydrate                             75-80    Cetyldimethylethyl ammonium bromide                             80-85    Tetraphenylphosphonium chloride                             75-80    ______________________________________

EXAMPLE 6

An example was run using the same procedure and recipe as in Example 3using cetyltrimethyl ammonium bromide except that potassium stearate wassubstituted for the sodium stearate.

    ______________________________________    Rheometer          M.sub.L  8.8    100 cpm, 190° C., 3°Arc                       M.sub.HF 54.1                       t'.sub.90 (min.)                                5.2    Mooney Viscometer  Min.     50    (Large Rotor)      Visc.    100° C.     t.sub.5 (min.)                                5.5                       t.sub.35 (min.)                                10.0    Compression set             37    Plied (%), 70 hours at 150° C.    ______________________________________

EXAMPLE 7

The following examples demonstrate the one-component curative system. Amaster batch having a recipe corresponding to that used in Example 3(except no stearic acid was added) was uniformly mixed in a Banburymixer. To this masterbatch was added 2 parts tetrabutyl ammoniumstearate per 100 parts polyacrylate. Mooney viscosity was determined forthe sample using the large rotor at 125° C. A Rheometer oscillating disctest was run using a microdie at 100 cpm, 190° C. with a 3 degree arc.Physical properties were determined on samples which had been cured forfour minutes at 190° C. In addition, compression set was determined onthe cured sample after 70 hours at 150° C. The test results are setforth below.

    ______________________________________    Mooney Viscometer, Large Rotor, 125° C.    Min. Visc.             73    t.sub.5 (min.)         1.6    t.sub.35 (min.)        2.0    Rheometer, Microdie, 100 cpm, 3° Arc, 190° C.    M.sub.L (lbf-in)       14.5    M.sub.HF (lbf-in)      52.5    t'.sub.90 (min.)       16.5    Original Physical Properties, Cured 4 min. at 190° C.    M100 (psi)             400    Ultimate Tensile Strength (psi at break)                           1700    Ultimate Elongation (percent)                           300    Hardness Durometer A   60    Compression Set, 70 hours at 150° C.    % Plied                80    ______________________________________

Thus, it is apparent that there has been provided, in accordance withthe invention, a method that fully satisfies the aims and advantages setforth above. While the invention has been described in conjunction withspecific embodiments thereof, it is evident that many alternatives,modifications, and variations will be apparent to those skilled in theart in light of the foregoing description. Accordingly, it is intendedto embrace all such alternatives, modifications, and variations as fallwithin the spirit and broad scope of the invention.

What is claimed is:
 1. A no-post-cure method of curing polyacrylaterubber having halogen and carboxy cure sites, comprising:mixing aneffective amount of a curative with said polyacrylate rubber until auniform vulcanizable composition results: said acrylate rubbercomprising(a) from about 40 percent to about 99.8 percent by weight ofan acrylate of the formula: ##STR7## wherein R is selected from thegroup consisting of an alkyl radical containing 1 to 18 carbon atoms, analkoxyalkyl, an alkylthioalkyl, and a cyanoalkyl radical containing 2 to12 carbon atoms; (b) from about 0.1 percent to about 30 percent byweight of a halogen-containing monomer selected from the groupconsisting of halogen-containing vinylene hydrocarbons andhalogen-containing vinyl monomers having the halogen group at least twocarbon atoms removed from an oxygen group; (c) from about 0.1 percent toabout 20 percent by weight of a carboxyl-containing monomer; and (d) upto about 35 percent by weight of a copolymerizable monomer containing aterminal vinylidene group; said curative comprising a metallic stearateand a quaternary salt selected from the class consisting of an ammoniumquaternary halogen salt, an ammonium quaternary hydroxide salt, aphosphonium quaternary halogen salt, and a phosphonium quarternaryhydroxide salt; processing said composition and maintaining saidcomposition below an activation temperature range prior to a curing stepwhereby said composition does not undergo any substantial amount of cureprior to said curing step, said activation temperature range being formabout 75° C. to about 85° C.,; and heating during said curing step saidcomposition to above an activation temperature range which causes saidcomposition to substantially cure whereby no-post-curing is necessaryand whereby said process permits large scale commercial production.
 2. Ano-post-cure method of curing polyacrylate rubber having halogen andcarboxyl cure sites, comprising:mixing an effective amount of a curativewith said polyacrylate rubber until a uniform vulcanizable compositionresults, said acrylate rubber comprising (a) from about 40 percent toabout 99.8 percent by weight of an acrylate of the formula: ##STR8##wherein R is selected from the group consisting of an alkyl radicalcontaining 1 to 18 carbon atoms, an alkoxyalkyl, an alkylthioalkyl, anda cyanoalkyl radical containing 2 to 12 carbon atoms; (b) from about 0.1percent to about 30 percent by weight of a halogen-containing monomerselected from the group consisting of halogen-containing vinylenehydrocarbons and halogen-containing vinyl monomers having the halogengroup at least two carbon atoms removed from an oxygen group; (c) fromabout 0.1 percent to about 20 percent by weight of a carboxyl-containingmonomer; and (d) up to about 35 percent by weight of a copolymerizablemonomer containing a terminal vinylidene group, said curative comprisinga metallic acid salt and a quaternary salt, said metallic acid saltbeing selected from the group consisting of carboxylic acids containingfrom 2 to about 24 carbon atoms and organophosphoric acids of theformula

    (R--O).sub.z PO.sub.y M

where M is an alkali metal, y equals 1 or 2, z equals 1 or 2, and y plusZ equals 3, and R is selected from the group consisting of alkylradicals containing from 1 to about 24 carbon atoms, and aryl radicalscontaining from 6 to about 24 carbon atoms and said quaternary saltbeing selected from the group consisting of an ammonium or phosphoniumquaternary salt of an anion X where X is an anion of an organic orinorganic acid wherein the acidic hydrogen is associated with a halogenor an oxygen atom; processing said composition and maintaining saidcomposition below an activation temperature range prior to a curing stepwhereby said composition does not undergo any substantial amount of cureprior to said curing step, said activation temperature range being fromabout 75° C. to about 85° C.,; and heating during said curing step saidcomposition above an activation temperature range which causes saidcomposition to substantially cure whereby no-post-cure is necessary, andwhereby said process permits large scale commercial production.
 3. Ano-post-cure method of curing polyacrylate rubber having halogen andcarboxyl cure sites, comprising:mixing an effective amount of a curativewith said polyacrylate rubber until a uniform vulcanizable compositionresults, said acrylate rubber comprising (a) from about 40 percent toabout 99.8 percent by weight of an acrylate of the formula: ##STR9##wherein R is selected from the group consisting of an alkyl radicalcontaining 1 to 18 carbon atoms, an alkoxyalkyl, an alkylthioalkyl, anda cyanoalkyl radical containing 2 to 12 carbon atoms; (b) from about 0.1percent to about 30 percent by weight of a halogen-containing monomerselected from the group consisting of halogen-containing vinylenehydrocarbons and halogen-containing vinyl monomers having the halogengroup at least two carbon atoms removed from an oxygen group; (c) fromabout 0.1 percent to about 20 percent by weight of a carboxyl-containingmonomer; and (d) up to about 35 percent by weight of a copolymerizablemonomer containing a terminal vinylidene group, said curative comprisinga metallic acid and a quaternary salt, said metallic acid salt beingselected from the group consisting of carboxylic acids containing from 2to about 24 carbon atoms and organophosphoric acids of the formula

    (R--O).sub.z PO.sub.y M

where M is an alkali metal, y equals 1 or 2, z equals 1 or 2, and y plusZ equals 3, and R is selected from the group consisting of alkylradicals containing from 1 to about 24 carbon atoms and aryl radicalscontaining from 6 to about 24 carbon atoms and said quaternary saltbeing selected from the group consisting of an ammonium or phosphoniumquaternary salt of an anion X where X is an anion of an organic orinorganic acid wherein the acidic hydrogen is associated with a halogenor an oxygen atom, said mixture having threshold temperaturecharacteristics, said threshold temperature characteristics including afirst area of uncured low minimum viscosity change being a change ofless than 150 Mooney units measured at 100° C. after a two week roomtemperature aging, said second area being a threshold temperature rangebeing the temperature at which time t₅ value as measured by the MooneyViscometer Large Rotor Test ASTM D1646 rises 5 points or more in 31minutes and a third cured area where the cured composition has a curedcompletion as measured by plied, compression set ASTM D395 after 70hours at 150° C. of equal to or less than 80 percent; and heating saidcomposition above an activation temperature range, said activationtemperature range being from about 75° C. to about 85° C., which causessaid composition to substantially cure whereby no-post-cure is necessaryand whereby said process permits large scale commercial production. 4.The method of claim 1 wherein said curative is present from about 0.1 toabout 25 parts by weight per 100 parts by weight of the rubber.
 5. Themethod of claim 2 wherein said curative is present from about 0.1 toabout 25 parts by weight per 100 parts by weight of the rubber.
 6. Themethod of claim 3 wherein said curative is present from about 0.1 toabout 25 parts by weight per 100 parts by weight of the rubber.
 7. Themethod of claim 1, further including the step of storing saidcomposition below said activation temperature range after said mixingstep and before said heating step, said storing step does not destroythe shelf stability of said composition.
 8. The method of claim 1,wherein said acrylate rubber comprises: (a) from about 65% to about99.6% by weight of an acrylate, wherein R is selected from the groupconsisting of alkyl radicals containing 1 to about 10 carbon atoms andalkoxyalkyl radicals containing 2 to about 8 carbon atoms; (b) fromabout 0.2% to about 15% by weight of a halogen-containing monomer; (c)from about 0.2 to about 10% by weight to a carboxyl containing monomer;and (d) up to about 10% by weight of a copolymerizable monomercontaining a terminal vinylidene group.
 9. The method of claim 8,wherein (a) is selected from the group consisting of ethyl acrylate,n-butyl acrylate, methoxyethyl acrylate, and ethoxyethyl acrylate; (b)is selected from the group consisting of vinyl chloroacetate, allylchloroacetate, 2-chloroethyl acrylate, 2-chloroethyl vinyl ether, vinylbenzyl chloride, 5-chloromethyl-2-norbornene, and5-chloroacetoxymethyl-2-norbornene; (c) is selected from the groupconsisting of acrylic acid, methacrylic acid; and itaconic acid; and (d)is selected from the group consisting of vinyl acetate, methylmethacrylate, ethyl methacrylate, styrene, acrylonitrile, acrylamide,and diethylene glycol diacrylate.
 10. The method of claim 1, whereinsaid curative comprises from about 0.5 parts to about 25 parts by weightbased upon 100 parts by weight of the rubber, of a quaternary salt ofthe formula: ##STR10## wherein Q is nitrogen or phosphorous, R₁, R₂, R₃,and R₄ are hydrocarbon radicals, containing 1 to about 18 carbon atomssuch as alkyl, aryl, alkaryl, aralkyl radicals, or wherein two or threeof the R₁, R₂, R₃, and R₄ form with nitrogen or phosphorous atom aheterocyclic structure containing 3 to 8 atoms selected form the groupconsisting of carbon, nitrogen, oxygen and sulfur, wherein at least twoatoms are carbon; and X is an ion such as chloride (Cl⁻), bromine (Br⁻),iodine (I⁻), or hydroxide (OH⁻).
 11. The method of claim 1, wherein saidmetallic stearate is selected from the class consisting of sodiumstearate or potassium stearate.
 12. The method of claim 10, wherein saidquaternary ammonium salts are selected from the class consisting oftetramethyl ammonium chloride, tetramethyl ammonium bromide,trimethylethyl ammonium iodide, trimethylsoya ammonium chloride,trimethylcetyl ammonium bromide, trimethylbenzyl ammonium chloride,dimethylethylcetyl ammonium chloride, dimethyloctylbenzyl ammoniumchloride, dimethyloleybenzyl ammonium chloride, dimethyloctadecylbenzylammonium chloride, dimethylphenylbenzyl ammonium bromide,dimethyldibenzyl ammonium bromide, methylethylpropylisobutyl ammoniumchloride, (tetradecyl)trimethyl ammonium chloride, methylcetyldibenzylammonium bromide, cetylpyridinium chloride, dodecylpyridinium bromide,tetrabutyl ammonium chloride, tetrabutyl ammonium bromide, tetrabutylammonium iodide, tetramethyl ammonium hydroxide pentahydrate,cetyldimethylethyl ammonium bromide, and myristyltrimethylammoniumbromide.
 13. The method of claim 10, wherein said quaternary phosphoniumsalts are selected from the class consisting of tetraphenyl phosphoniumbromide, hexadecyltributyl phosphonium bromide, tetraphenyl phosphoniumchloride, tetraphenyl phosphonium iodide, tetrabutyl phosphoniumchloride, tetrabutyl phosphonium bromide, triphenylbenzyl phosphoniumchloride, triphenylbenzyl phosphonium bromide, triphenylbenzylphosphonium iodide, triphenylmethoxymethyl phosphonium chloride,triethylbenzyl phosphonium chloride, and tricyclohexylbenzyl phosphoniumchloride.
 14. A method of claim 2 wherein X is selected from the groupconsisting of Cl⁻, Br⁻, I⁻, HSO₄ ⁻, H₂ PO₄ ⁻, RCOO⁻, ROSO₃ ⁻, RSO₃ ⁻,and ROPO₃ H⁻ where R is an alkyl or alkaryl radical containing 1 to 18carbon atoms.
 15. A method of claim 3, wherein said thresholdtemperature characteristics include a first area of uncured low minimumviscosity change being a change of less than 150 Mooney units measuredat 100° C. after a two week room temperature aging, a second area ofcuring at the threshold temperature range and a third cured area wherethe cured composition has a cure completion measured by plied,compression set ASTM D395 after 70 hours at 150° C. of equal to or lessthan 80%.
 16. A method of claim 15, wherein said first area of uncuredlow minimum viscosity change is a change of less than 5 Mooney unitsmeasured at 100° C. after an eight week room temperature aging and saidthird cured area has a cure completion as measured by compression setequal to or less than 40%.